1. Field of the Invention
The subject matter described herein relates generally to a system and method for meeting end conditions determined by a continuous time path planning method for motion control systems, more particularly path planners.
2. Related Art
Path planners or path generators typically comprise motion controllers that are used to control motors. The motors that employ path planning can be found in various industrial systems such as manufacturing, assembling, packaging and other capacities. These motors typically control the movements of elements such as drill bits or robotic arms. Path generators determine the movements of the controlled elements.
Path generators use various kinetic path algorithms along with discrete time controllers. The use of discrete time controllers with continuous time path planning algorithms creates problems for meeting the end conditions of the path plan. The path plan is comprised of movements that are determined on a continuous basis and not within a sampling period. A discrete time controller is limited to outputting data on a predetermined sampling period. An example of a problem that arises in the above situation is that the determined movement may be an end condition such as an instruction to halt at a point in time that occurs before the next sampling period. This problem can result in the discrete time controller not instructing the motor to halt before the next sample period, possibly resulting a less desirable path being followed that violates the constraints of the move, for example.
Prior path generators implemented a compensation scheme that altered the initial conditions at the start of deceleration such that the end conditions would be reached on an even sample period, e.g. every 5 ms. Although computationally desirable, it is not desirable to the controller application because it introduces an uncontrolled step change to the output at that point. This creates a discontinuity in the planned path. Similarly, other known time compensation schemes are undesirable due to significant increases in computational load.
Accordingly, there is a need for a more accurate, improved time compensation scheme when utilizing a continuous time path planning with a discrete time controller to meet end conditions.